| 摘要 |
PROBLEM TO BE SOLVED: To prevent peeling and crack in an insulation layer and a copper foil by forming connection between a large diameter part conductor layer and an in-layer direction circuit in a position wherein a diameter starts to decrease from a large diameter part to a board thickness direction small diameter circuit. SOLUTION: A base 3 is arranged in each third layer from an uppermost layer and a lowermost layer and an in-layer direction circuit is formed therebetween. Five such bases are arranged and heated at 170 deg.C and a pressure of 4MPa for 60 minutes by using a prepreg 4 between the bases for lamination and bonding. A front to rear through hole 10 is shaped by a drill of a diameter of 0.3mm, a large diameter hole 14 is shaped to a depth wherein a shoulder part of a drill reaches an inner layer pad 6 by a drill of a diameter of 0.73mm, chemical copper plating is applied and a conductor layer 5 of a substrate thickness direction circuit large diameter part and a conductor layer 7 of a small diameter part are formed. Therefore, if connection of an in-layer direction circuit to the inner layer pad 6 is formed in a position wherein a conductor layer diameter starts to decrease for connecting the conductor layers 5, 7, peeling and breakdown caused by concentration of thermal stress during solder heating mounting can be prevented. |
